I have a Listbox, where I want to load in different types of UserControls in a UWP app.
The reason I need UserControls is because there is code-behind needed for every item that will be shown in the list, so a simple DataTemplate doesn't cut it.
I'm getting an error on the line
<converters:HomeWidgetControlPicker>
in the listbox.
The specified value cannot be assigned. The following type was expected: "DependencyObject".
How can I make the UserControl load? I used this method in an older UWP app and there it worked, but in my new project it doesn't.
I cannot use x:DataType as all items that will be of the same class (HomeWidget), but depending on the Type property of HomeWidget the correct UserControl is selected.
I made a DataTemplateSelector:
public class HomeWidgetControlPicker : DataTemplateSelector
{
public DataTemplate Artist { get; set; }
public DataTemplate Release { get; set; }
protected override DataTemplate SelectTemplateCore(object item, DependencyObject container)
{
if (item != null)
{
var result = (HomeWidget)item;
if (result.Type == "artist")
{
return Artist;
}
if (result.Type == "release")
{
return Release;
}
}
return null;
}
}
and I have a Listbox, currently only type (HomeWidgetControlPicker.Artist) is used, but more will follow.
<ListBox x:Name="wrapGrid" ItemContainerStyle="{StaticResource WrapPanelBorderedItem}" ItemsSource="{x:Bind WidgetList}" Background="{x:Null}" ScrollViewer.VerticalScrollBarVisibility="Disabled" VerticalAlignment="Top" HorizontalAlignment="Center" >
<ListBox.ItemsPanel>
<ItemsPanelTemplate>
<userControls:WrapPanel/>
</ItemsPanelTemplate>
</ListBox.ItemsPanel>
<ListBox.ItemTemplate>
<DataTemplate>
<converters:HomeWidgetControlPicker>
<converters:HomeWidgetControlPicker.Artist>
<DataTemplate>
<homeItems:HomeArtist></homeItems:HomeArtist>
</DataTemplate>
</converters:HomeWidgetControlPicker.Artist>
</converters:HomeWidgetControlPicker>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
The way you are using DataTemplateSelector
should be wrong. In your code snippet, DataTemplateSelector
is placed as the root element of DataTemplate
, but actually, you can use a DataTemplateSelector
and set properties such as ItemTemplateSelector
to assign it to a data view. See remarks section of DataTemplateSelector
class for more details.
The base DataTemplateSelector class is not used as an object element in XAML. However, it is a common scenario to derive a custom DataTemplateSelector, map a xmlns prefix for the custom class and its namespace/assembly, and then refer to an instance of the custom class as defined in a Resources block in XAML. This makes it possible to refer to the custom template selector class by x:Key, and use that reference to set the value of properties such as ItemTemplateSelector in XAML templates and visual states.
For example:
<Page.Resources>
<DataTemplate x:Key="Artist" x:DataType="local:HomeWidget">
<Grid>
<local:UserControl1></local:UserControl1>
...
</Grid>
</DataTemplate>
<DataTemplate x:Key="Release" x:DataType="local:HomeWidget">
<Grid>
<local:UserControl2></local:UserControl2>
...
</Grid>
</DataTemplate>
<local:HomeWidgetControlPicker x:Key="HomeWidgetControlPicker" Artist="{StaticResource Artist}" Release="{StaticResource Release}">
</local:HomeWidgetControlPicker>
</Page.Resources>
<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
<ListBox x:Name="wrapGrid" ItemTemplateSelector="{StaticResource HomeWidgetControlPicker}" ItemsSource="{x:Bind WidgetList}"
...
</ListBox>
</Grid>